1. Field of the Invention
The present invention relates to an ophthalmic imaging apparatus which images an eye to be examined, a method of controlling the ophthalmic imaging apparatus, and a storage medium.
2. Description of the Related Art
Currently, various types of ophthalmic apparatuses using optical apparatuses are used. For example, various types of apparatuses such as an anterior ocular segment imaging apparatus, fundus camera, and scanning laser ophthalmoscope (SLO) are used as optical apparatuses for observing the eyes. Of these apparatuses, an optical tomography apparatus based on optical coherence tomography (OCT) using multiwavelength interference is an apparatus capable of obtaining a tomographic image of a sample with a high resolution. This apparatus has been becoming indispensable as an ophthalmic apparatus for out-patient clinics dedicated to retinal diseases. This apparatus will be referred to as an OCT apparatus hereinafter.
An OCT apparatus can measure a slice of an object to be examined by splitting measurement light which is low-coherent light into reference light and measurement light, irradiating the object with the measurement light, and making return light from the object interfere with the reference light. The OCT apparatus can obtain a high-resolution tomographic image by scanning measurement light on a sample. This apparatus therefore obtains a tomographic image of the retina of the fundus of the eye to be examined, and is widely used for ophthalmic diagnosis of the retina. If, however, the object to be examined is a living organism like the eye, the distortion of an image due to the movement of the eye poses a problem. Demands have therefore risen for high-speed, high-sensitivity measurement.
Japanese Patent Laid-Open No. 2009-523563 has proposed an OCT apparatus which obtains OCT images corresponding to scan patterns used for scanning of a plurality of portions. A scan pattern consists of a plurality of concentric circles and a plurality of radial lines.
Japanese Patent Laid-Open No. 2010-110392 has proposed an OCT apparatus which performs addition processing of a plurality of tomographic images obtained by imaging the same region and averaging pixel values to reduce the influence of noise which occurs irregularly. At this time, the OCT apparatus segments a captured image into a plurality of regions, and detects positional shift information between the respective captured images for each segmented region. The apparatus then performs correction for each segmented region based on the positional shift information, and averages the respective corrected images.
Although the OCT apparatus disclosed in Japanese Patent Laid-Open No. 2009-523563 has a scan pattern for scanning a plurality of areas obtained by segmenting a captured image, the apparatus does not perform averaging processing. This poses a problem: the obtained tomographic image is affected by irregular noise.
The OCT apparatus disclosed in Japanese Patent Laid-Open No. 2010-110392 averages a plurality of images captured in the same area to reduce the influence of irregular noise, and performs averaging processing of pixel values. The number of tomographic images to be obtained for the execution of this averaging processing is uniformly fixed. To perform averaging processing, it is necessary to capture a plurality of images in the same area. To obtain high-quality tomographic images, it is necessary to obtain a larger number of tomographic images. Although a captured image is segmented into a plurality of areas, averaging processing is not performed for each imaging area. In practice, therefore, unnecessary tomographic images may be obtained. This will lead to a longer imaging time and hence place a burden on an object to be examined.
In consideration of the above problems, the present invention provides a technique of shortening the time required for imaging and reducing the burden on a patient by decreasing the number of images to be obtained to obtain a high-quality tomographic image necessary for diagnosis.